Hot stamping is the heat transfer of a pigmented color or metallized surface from a polyester carrier onto a thermoplastic substrate. A heated die or roller is used to apply pressure to a foil. The pressure forces the pigmented or metallized portion of foil into contact with the plastic substrate. The combination of heat and pressure softens the plastic substrate and activates the foil coating to form a strong chemical physical bond. When the foil is pulled away, only the areas subjected to the hot stamp remain affixed to the plastic substrate. A vertical stamping or roll-on machine is used for the operation. The vertical stamping machine contains a heated die of brass, steel or silicone rubber to transfer an area or a specific pattern as each part is placed in position. Roll-on methods utilize a silicone rubber roller or arced die to apply the foil in a continuous or batch process. Hot stamping is an efficient, inexpensive way to apply decoration to thermoplastic substrates. Hot stamping of this nature cannot be used with glass, however, because glass melts at a much higher temperature than most thermoplastic materials.
Generally decoration in the form of gold leaf, color design, or printing, etc. is applied to glass by a glazing process similar to that used with ceramics. For example, in gold leafing the gold decoration is applied to the glass container by a variety of methods such as silk screen, printing, etc. The container is then subjected to extremely high kiln temperatures and the decoration is, in essence, baked on. Unfortunately this process is time consuming, expensive, energy intensive, and subject to safety considerations due to the high temperatures and gases necessary to operate the kilns.
There is thus a great need for a simple, economical and ultra-safe procedure for applying decoration to glass substrates.